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This research aims to construct a prototype of an x-ray backscatter detector using MPPC for clearer image detection in cargo scanning systems. The objectives include testing the prototype and estimating detector resolution.
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FINAL YEAR PROJECT4SSCZ Progress Presentation NURDYANA BINTI RAMLEE NUR FATIN NASUHA BINTI JAAFAR
PROBLEM STATEMENT • In cargo scanning system, the image form was not clear when detect transmission x-ray only. • To get clear image, backscatter x-ray must be detect. • In this project, backscatter x-ray represent as photon will be detect by using MPPC.
OBJECTIVES The main objectives of this research are as follows: • To construct the prototype of x-ray backscatter detector using MPPC. • Test the prototype using alpha, beta, gamma and x-ray source. • To measure the backscatter x-ray that represent as photon. • To estimate and determine the detector resolution.
WHAT IS BACKSCATTER X-RAY? The collision of a photon by a charged particle, usually an electron. It results in a decrease in energy (increase in wavelength) of the photon (which may be an X ray or gamma ray photon), called the Compton effect. • Backscatter x-ray is produced from Compton Scattering process. • In cargo scanning system, the energy of incident photon (x-ray) is higher than binding energy of atomic electron, then can treat the electron as free electron. • This technique involves positioning both source and detection apparatus on only one side of a target object.
MPPC DETECTOR • Multi-Pixel Photon Counter ( MPPC ) is a new type of photodetector device developed by Hamamatsu Photonics. • Is a Si-PM (silicon photomultiplier) device Sensitive area of MPPC detector
EASIROC-NIM MODULE • EASIROC-NIM MODULE is an optical measurement modules • Capable of measuring light over a wide range of light levels (10 orders of magnitude) • This module is equipped with a chip called EASIROC. EASIROC stands for Extended Analogue SI-pm ReadOut Chip is a 32 channels fully analogue front end ASIC dedicated to readout SiPM detectors.
Observing pulse Figure shows the pulse waveforms when using a linear amplifier
When light enters the MPPC at variable time The number of photons detected within a certain time period can be estimated by integrating the MPPC output Using intergrating amplifier Figure shows a distribution plotted for the amount of charge accumulated in the intergration time Intergrating the output charge
FeaturesLow afterpulses • new MPPC reduced afterpulses due to use of improved materials and wafer process technologies. • Reduces the generation of delayed output signal
Low crosstalk • Lower the generation of other pulses by affected pixels
HIGH PHOTON DETECTION EFFICIENCY Graph of Photon detection efficiency(%) vs Overvoltage(V) The table shows some recommended overvoltage.